編輯：關於Android編程
其實，這一部分，總的來說，主要寫DBOpenHelper類和PersonDao類即可。。。。
其中DBOpenHelper主要封裝了數據庫的創建、表的創建與修改。。而PersonDao主要封裝對表的DAO操作。。。。
1、DBOpenHelper
package com.example.sqlitetest;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBOpenHelper extends SQLiteOpenHelper {
public DBOpenHelper(Context context){//父類沒有無參構造函數,必須顯示調用有參構造函數.
/*
* 由於父類沒有無參構造函數, 必須顯式調用有參的構造函數
* 參數1: 上下文環境, 用來確定數據庫文件存儲的目錄..創建的數據庫存在於/data/data/應用的報名/databases/xxx.db
* 參數2: 數據庫文件的名字
* 參數3: 生成游標的工廠, 填null就是使用默認的
* 參數4: 數據庫的版本, 從1開始
*/
super(context,njupt.db,null,2);
}
/**
* 一般來說,創建表的代碼放在onCreate()中
*/
@Override
public void onCreate(SQLiteDatabase db) {
System.out.println(----------->onCreate);
db.execSQL(CREATE TABLE person(id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR(20))); // 執行SQL語句, 創建表
}
/**
* 修改表的代碼放在onUpdate()中...
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
System.out.println(---------->onUpdate);
db.execSQL(ALTER TABLE person ADD balance INTEGER);
}
}
2、PersonDao
package com.example.sqlitetest;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
public class PersonDao {
private Context context;
private DBOpenHelper helper;
public PersonDao(Context context) {
this.context = context;
helper = new DBOpenHelper(context);
}
public void insert(Person p){
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(INSERT INTO person(name, balance) VALUES(?, ?), new Object[] { p.getName(), p.getBalance() }); // 執行SQL語句, 插入
db.close();
}
public void delete(int id){
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(DELETE FROM person WHERE id=?, new Object[]{id});
db.close();
}
public void update(Person p){
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(UPDATE person SET name=?, balance=? WHERE id=?, new Object[]{p.getName(),p.getBalance(),p.getId()});
db.close();
}
public Person query(int id){
SQLiteDatabase db = helper.getReadableDatabase();//獲取數據庫連接,可讀的
Cursor c = db.rawQuery(SELECT name, balance FROM person WHERE id=?, new String[]{id + });
Person p = null;
if(c.moveToNext()){//判斷游標是否包含下一條記錄,如果包含,將游標向後移一位
String name = c.getString(0);//獲取0號索引上的數據,轉換為String類型
// String name = c.getString(c.getColumnIndex(name));//這種方法也是極好的
int balance = c.getInt(1);
p = new Person(id, name, balance);
}
c.close();
db.close();
return p;
}
public List queryAll(){
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(SELECT id, name, balance FROM person, null);
List persons = new ArrayList();
while(c.moveToNext()){
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
public int queryCount(){
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(SELECT COUNT(*) FROM person, null);
c.moveToNext();
int count = c.getInt(0);
c.close();
db.close();
return count;
}
public List queryPage(int pageNum,int capacity){
String offset = (pageNum - 1)*capacity + ;
String len = capacity + ;
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(SELECT id, name, balance FROM person LIMIT ?,?, new String[]{offset,len});
List persons = new ArrayList();
while(c.moveToNext()){
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
/**
* 數據庫的事務
*
* 從from這個賬戶匯款到to這個賬戶,匯amount這個多錢
* @param from
* @param to
* @param amount
*/
public void remit(int from,int to,int amount){
SQLiteDatabase db = helper.getWritableDatabase();
try{
db.beginTransaction();//開始事務
db.execSQL(UPDATE person SET balance=balance-? WHERE id=?, new Object[] { amount, from });
db.execSQL(UPDATE person SET balance=balance+? WHERE id=?, new Object[] { amount, to });
db.setTransactionSuccessful();//設置事務成功點...結束事務的時候執行成功點之前的sql語句
}finally{
db.endTransaction();//結束事務
db.close();
}
}
}
3、Person
package com.example.sqlitetest;
public class Person {
private Integer id;
private String name;
private Integer balance;
public Person() {
super();
}
public Person(Integer id, String name, Integer balance) {
super();
this.id = id;
this.name = name;
this.balance = balance;
}
@Override
public String toString() {
return Person [id= + id + , name= + name + , balance= + balance
+ ];
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getBalance() {
return balance;
}
public void setBalance(Integer balance) {
this.balance = balance;
}
}
4、DBTest
package com.example.sqlitetest;
import java.util.List;
import android.test.AndroidTestCase;
public class DBTest extends AndroidTestCase {
public void testCreateDB(){
DBOpenHelper helper = new DBOpenHelper(getContext());
helper.getWritableDatabase();
}
public void testInsert(){
PersonDao dao = new PersonDao(getContext());
for(int i = 1 ; i < 100 ; ++i){
dao.insert(new Person(i,hjd + i , 45000+i));
}
// dao.insert(new Person(2, hjd, 40000));
}
public void testDelete(){
PersonDao dao = new PersonDao(getContext());
dao.delete(1);
}
public void testUpdate(){
PersonDao dao = new PersonDao(getContext());
Person p = new Person(2, zzt, 10000);
dao.update(p);
}
public void testQuery(){
PersonDao dao = new PersonDao(getContext());
System.out.println(dao.query(2));
}
public void testQueryAll(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryAll();
for(Person p : persons){
System.out.println(p);
}
}
public void testQueryCount(){
PersonDao dao = new PersonDao(getContext());
System.out.println(---------> + dao.queryCount());
}
public void testQueryPage(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryPage(5, 10);
for(Person p : persons){
System.out.println(p);
}
}
}
5、MainActivity
package com.example.sqlitetest;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
以上的PersonDao中所使用到的增刪改查的實現方法都是需要直接寫sql，其實還有一種方式來實現增刪改查。
其實其底層實現也是將穿的哪些參數拼成sql語句的。。
以下將完整的PersonDao和DBTest貼出來
PersonDao
package com.example.sqlitetest;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
public class PersonDao {
private Context context;
private DBOpenHelper helper;
public PersonDao(Context context) {
this.context = context;
helper = new DBOpenHelper(context);
}
public void insert(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(INSERT INTO person(name, balance) VALUES(?, ?),
new Object[] { p.getName(), p.getBalance() }); // 執行SQL語句, 插入
db.close();
}
/**
* 某些情況之下程序會接受一個ContentValues,這時候采用這種存儲方式比較方便...
* @param p
*/
public void insert1(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();
/**
* ContentValues:類似於Map,鍵放列名,值放要插入的內容...
* 為什麼說ContentValues類似於Map,其實看他的成員變量及put方法就知道了 Adds a value to the set.
*
* @param key
* the name of the value to put
* @param value
* the data for the value to put
*
* public void put(String key, String value) {
* mValues.put(key, value); }
*/
ContentValues values = new ContentValues();
values.put(name, p.getName());
values.put(balance, p.getName());
/**
* 第二個參數隨便寫一個列名,用於處理values值為空的情況..因為列名不能為null
*/
db.insert(person, name, values);//其實它底層也是采用拼SQL語句的方式的.返回插入的id是多少
db.close();
}
public void delete(int id) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(DELETE FROM person WHERE id=?, new Object[] { id });
db.close();
}
public void delete1(int id){
SQLiteDatabase db = helper.getWritableDatabase();
db.delete(person, id=?, new String[]{id + });
db.close();
}
public void update(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL(UPDATE person SET name=?, balance=? WHERE id=?,
new Object[] { p.getName(), p.getBalance(), p.getId() });
db.close();
}
public void update1(Person p){
SQLiteDatabase db = helper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(name, p.getName());
values.put(balance, p.getBalance());
db.update(person, values, id=?, new String[]{p.getId() + });
db.close();
}
public Person query(int id) {
SQLiteDatabase db = helper.getReadableDatabase();// 獲取數據庫連接,可讀的
Cursor c = db.rawQuery(SELECT name, balance FROM person WHERE id=?,
new String[] { id + });
Person p = null;
if (c.moveToNext()) {// 判斷游標是否包含下一條記錄,如果包含,將游標向後移一位
String name = c.getString(0);// 獲取0號索引上的數據,轉換為String類型
// String name = c.getString(c.getColumnIndex(name));//這種方法也是極好的
int balance = c.getInt(1);
p = new Person(id, name, balance);
}
c.close();
db.close();
return p;
}
public Person query1(int id){
SQLiteDatabase db = helper.getReadableDatabase();// 獲取數據庫連接,可讀的
// Cursor c = db.rawQuery(SELECT name, balance FROM person WHERE id=?,
// new String[] { id + });
/**
* db.query(表名,需要查詢的列名,查詢條件,查詢條件的參數,group by,having,order by);
*/
Cursor c = db.query(person, new String[]{name,balance}, id=?, new String[]{id + }, null, null, null);
Person p = null;
if (c.moveToNext()) {// 判斷游標是否包含下一條記錄,如果包含,將游標向後移一位
String name = c.getString(0);// 獲取0號索引上的數據,轉換為String類型
// String name = c.getString(c.getColumnIndex(name));//這種方法也是極好的
int balance = c.getInt(1);
p = new Person(id, name, balance);
}
c.close();
db.close();
return p;
}
public List queryAll() {
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(SELECT id, name, balance FROM person, null);
List persons = new ArrayList();
while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
public List queryAll1(){
SQLiteDatabase db = helper.getReadableDatabase();
// Cursor c = db.rawQuery(SELECT id, name, balance FROM person, null);
Cursor c = db.query(person, null, null, null, null, null, id DESC);
List persons = new ArrayList();
while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
public int queryCount() {
SQLiteDatabase db = helper.getReadableDatabase();
// Cursor c = db.rawQuery(SELECT COUNT(*) FROM person, null);
Cursor c = db.query(person, new String[]{COUNT(*)}, null, null, null, null, null);
c.moveToNext();
int count = c.getInt(0);
c.close();
db.close();
return count;
}
public int queryCount1(){
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(SELECT COUNT(*) FROM person, null);
c.moveToNext();
int count = c.getInt(0);
c.close();
db.close();
return count;
}
public List queryPage(int pageNum, int capacity) {
String offset = (pageNum - 1) * capacity + ;
String len = capacity + ;
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery(
SELECT id, name, balance FROM person LIMIT ?,?, new String[] {
offset, len });
List persons = new ArrayList();
while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
public List queryPage1(int pageNum,int capacity){
String offset = (pageNum - 1) * capacity + ;
String len = capacity + ;
SQLiteDatabase db = helper.getReadableDatabase();
// Cursor c = db.rawQuery(
// SELECT id, name, balance FROM person LIMIT ?,?, new String[] {
// offset, len });
Cursor c = db.query(person,null, null, null, null, null, null,offset + , + len);
List persons = new ArrayList();
while (c.moveToNext()) {
Person p = new Person(c.getInt(0), c.getString(1), c.getInt(2));
persons.add(p);
}
c.close();
db.close();
return persons;
}
/**
* 數據庫的事務
*
* 從from這個賬戶匯款到to這個賬戶,匯amount這個多錢
*
* @param from
* @param to
* @param amount
*/
public void remit(int from, int to, int amount) {
SQLiteDatabase db = helper.getWritableDatabase();
try {
db.beginTransaction();// 開始事務
db.execSQL(UPDATE person SET balance=balance-? WHERE id=?,
new Object[] { amount, from });
db.execSQL(UPDATE person SET balance=balance+? WHERE id=?,
new Object[] { amount, to });
db.setTransactionSuccessful();// 設置事務成功點...結束事務的時候執行成功點之前的sql語句
} finally {
db.endTransaction();// 結束事務
db.close();
}
}
}
DBTest
package com.example.sqlitetest;
import java.util.List;
import android.test.AndroidTestCase;
public class DBTest extends AndroidTestCase {
public void testCreateDB(){
DBOpenHelper helper = new DBOpenHelper(getContext());
helper.getWritableDatabase();
}
/**
* 需要注意的是，在這個例子中,person表中的id是自增的....不收Person中的id這個成員變量影響...
*/
public void testInsert(){
PersonDao dao = new PersonDao(getContext());
for(int i = 1 ; i < 100 ; ++i){
dao.insert(new Person(i,hjd + i , 45000+i));
}
// dao.insert(new Person(2, hjd, 40000));
}
public void testInsert1(){
PersonDao dao = new PersonDao(getContext());
for(int i = 0 ; i < 100 ; ++i){
dao.insert1(new Person(i, hjd + i, 30000));
}
// dao.insert1(new Person(3, dzdp, 10000));
}
public void testDelete(){
PersonDao dao = new PersonDao(getContext());
dao.delete(1);
}
public void testDelete1(){
PersonDao dao = new PersonDao(getContext());
dao.delete1(1);
}
public void testUpdate(){
PersonDao dao = new PersonDao(getContext());
Person p = new Person(2, zzt, 10000);
dao.update(p);
}
public void testUPdate1(){
PersonDao dao = new PersonDao(getContext());
Person p = new Person(2, hjd, 40000);
dao.update1(p);
}
public void testQuery(){
PersonDao dao = new PersonDao(getContext());
System.out.println(dao.query(2));
}
public void testQuery1(){
PersonDao dao = new PersonDao(getContext());
System.out.println(------------> + dao.query1(2));
}
public void testQueryAll(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryAll();
for(Person p : persons){
System.out.println(p);
}
}
public void testQueryAll1(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryAll1();
for(Person p : persons){
System.out.println( -----------> + p);
}
}
public void testQueryCount(){
PersonDao dao = new PersonDao(getContext());
System.out.println(---------> + dao.queryCount());
}
public void testQueryCount1(){
PersonDao dao = new PersonDao(getContext());
System.out.println(------->queryCount1: + dao.queryCount1());
}
public void testQueryPage(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryPage(5, 10);
for(Person p : persons){
System.out.println(p);
}
}
public void testQueryPage1(){
PersonDao dao = new PersonDao(getContext());
List persons = dao.queryPage1(2, 10);
for(Person p : persons){
System.out.println(---------> + p);
}
}
}
Android實現把文件存放在SDCard的方法
本文實例講述了Android實現把文件存放在SDCard的方法。分享給大家供大家參考。具體如下：使用Activity的openFileOutput()方法保存文件，文件是
Android開發之自定義View專題（一）：自定義柱形圖
博主之前做的項目中，需要用到報表功能，之前在網上百度谷歌各種結果，沒有一個是能夠滿足博主的老板的需求的，無奈之前博主只好自己去研究。終於研究出了一個不錯的結果。先上效果圖
安卓程序開發入門
創建一個新項目是很簡單的，只要你安裝了Eclipse插件，並且你的Eclipse軟件版本在3.2或3.3，你就可以開始開發了。 首先, 看一下要創建"Hell
Android 高仿QQ 沉浸式狀態欄
前言：在進入今天正題前，還是老樣子先談談感想吧，最近感覺整個都失去了方向感，好迷茫！找工作又失敗了，難道Android真的飽和了？這兩天我一直沒出門，除了下樓哪外賣就是宅
